Afterburner fuel manifold flow sensor and igniter control

ABSTRACT

Apparatus for sensing the rate of fuel flow into an afterburner fuel manifold and energizing ignition apparatus for a predetermined time interval to ignite the after afterburner fuel flow when the manifold is filled to a predetermined extent as well as providing a simultaneous output signal to release the gates of a variable area exhaust nozzle downstream from the afterburner.

United States Patent McCombs, Jr.

[ 1 Sept. 12, 1972 [54] AFTERBURNER FUEL MANIFOLD FLOW SENSOR ANDIGNITER CONTROL Howard L. McCombs, Jr., 717 N. Bendix Dr., South Bend,1nd. 46628 Filed: July 15, 1971 App1.No.: 162,883

Inventor:

US. Cl. ..60/39.82 R, 60/241 Int. Cl. ..F02c 7/26 Field of Search..60/39.82 R, 39.82, 241, 261;

References Cited UNITED STATES PATENTS 9/ 1958 Trowbridge ..60/39.82 S

will/III 2,722,800 11/1955 .lubbetal. ..60/241 2,885,857 5/1959 Hemlock..60/39.82L

Primary ExaminerCarlton R. Croyle Assistant ExaminerRobert E. GarrettAttorney-Gordon H. Chenez et a1.

[57] ABSTRACT Apparatus for sensing the rate of fuel flow into anafterbumer fuel manifold and energizing ignition apparatus for apredetermined time interval to ignite the after afterbumer fuel flowwhen the manifold is filled to a predetermined extent as well asproviding a simultaneous output signal to release the gates of avariable area exhaust nozzle downstream from the afterbumer.

7 Claims, 9 Drawing Figures PATENTED EPIZ m2 3.690.094

SHEET 1 BF 9 INVENTOR.

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AGENT PATENTED SEP 12 1912 SHEET 2 6? 9 PATENTEDSEP 12 m2 SHEET 3 OF 9ma 3m NEW mww BY w? n u.

PATENTEBSEP 12 m2 SHEET 5 OF .9

AFTERBURNER FUEL MANIFOLD FLOW SENSOR AND IGNITER CONTROL Thisapplication is a division of copending application Ser. No. 782,012,filed Dec. 3, 1968, now US. Pat. No. 3,611,802.

The conventional afterburner ignition apparatus of which I am aware isnot entirely satisfactory due to a failure thereof to accurately andreliably sense the extent to which the afterburner fuel manifold isfilled with fuel so that the afterburner fuel flow ignition occurs atthe optimum afterburner fuel-air ratio. If afterbumer' fuel ignitiondoes not occur at the proper afterburner fuel-air ratio, a number ofundesirable events may occur among which are overfueling or underfuelingof the afterburner with resulting ignition failure, incompletecombustion resulting from inadequate flame propagation through theafterburner fuel-air mixture, lack of control over the thrust bumpgenerated as a result of afterburner ignition and waste of significantportions of unburned afterburner fuel.

The above-mentioned unsatisfactory operation is, in part, due to themanner in which the conventional apparatus senses the degree of manifoldfuel fill which cannot be relied on as an accurate and reliableindication under all conditions of engine operation. For instance, it iscommon to sense manifold fuel pressure as an indication of the volume offuel therein. However, an afterburner fuel manifold is normally heatedto a relatively high temperature by the hot motive gas flow impingingthe same at all times during engine operation with the afterburnerinoperative such that, upon initiating afterburner fuel flow to themanifold, the resulting flashing of fuel therein produces excesspressure which cannot be relied on as a true indication of the extent towhich the manifold is filled with liquid fuel.

Furthermore, in the case of conventional ignition apparatus of thewell-known hot streak ignition type wherein a predetermined excessquantity of fuel injected into the main combustion chamber of the enginepasses through the gas turbine in flame form to ignite the afterburnerfuel flow the requirement for proper afterburner fuel conditions isextremely important due to the short interval of time during which thehot streak exists. Recycling of the hot streak in the event ofafterburner ignition failure may not be immediately available such that,under emergency conditions requiring immediate afterburner operation,the failure may not be rectified in time to avert loss of aircraftand/or human life.

It is, therefore, an object of the present invention to provideafterburner fuel flow sensing and igniting apparatus which is accurateand reliable in operation.

It is another object of the present invention to provide afterburnerfuel manifold flow sensing apparatus which is insensitive to pressureconditions in the fuel manifold per se which may provide unreliablepressure signals.

Other objects and advantages of the present invention may becomeapparent from the following description and accompanying drawingswherein:

FIG. 1 represents a schematic illustration of a gas turbine engineequipped with an afterburner and variable exhaust nozzle and controlsystem therefor embodying the present invention;

FIG. 2 is a sectional schematic of the afterburner fuel manifold flowsensing and igniter control of FIG. 1 embodying the present invention;

FIG. 3 is a sectional schematic similar to FIG. 2 but showing thepositions assumed by the various component portions thereof during fuelmanifold filling operation;

FIG. 4 is a sectional schematic similar to FIG. 2 but showing thepositions assumed by the various component portions thereof during afirst cycle of afterburner ignition operation;

FIG. 5 is a sectional schematic similar to FIG. 2 but showing thepositions assumed by the various component portions thereof during asecond cycle of afterburner ignition operation;

FIG. 6 is a sectional schematic similar to FIG. 2 but showing thepositions assumed by the various component portions thereof subsequentto ignition of the afterburner;

FIG. 7 is a sectional schematic similar to FIG. 2 but showing thepositions assumed by the various component portions thereof duringafterburner operation;

FIG. 8 is a sectional schematic similar to FIG. 2 but showing thepositions assumed by the various component portions thereof followingafterburner shut down;

FIG. 9 is a sectional schematic similar to FIG. 1 but showing a modifiedform of a portion thereof.

Referring to FIG. 1, numeral 20 designates a conventional aircraft gasturbine engine provided with a casing 22 defining an air inlet 24 andexhaust nozzle 26. Air entering inlet 24 is received by an aircompressor 28 and discharged to one or more combustion chambers 30 fromwhich hot motive gas is discharged to a gas turbine 32 which is fixedlysecured via a shaft 34 to compressor 28 to rotatably drive the same.Conventional fuel control apparatus, not shown, is connected to supplymetered fuel to a fuel manifold 36 having fuel injection nozzlesgenerally indicated by 38 connected to inject fuel into combustionchambers 30. An afterburner fuel manifold 40 in casing 22 downstreamfrom turbine 32 is provided with injection nozzles 42 which spray fuelto the gas exhausted from turbine 32. The resulting afterburner air-fuelmixture is burned to raise the temperature of the gas accordingly andthus increase the propelling thrust derived from the gas which expandsthrough exhaust nozzle 26 to the atmosphere. The effective flow area ofexhaust nozzle 26 is controlled by movable gates 44 suitably connectedto casing 22 and actuated by motor means generally indicated by 46 inresponse to output signals generated by a conventional exhaust nozzlecontrol generally indicated by 48 as a function of selected inputsignals generated by engine operating variable conditions and imposed onexhaust nozzle control 48 as will be recognized by those skilled in theart.

The afterburner fuel manifold 40 is supplied pressurized fuel via asupply conduit 50 leading from a pressurized fuel source 52. An enginedriven fuel pump 53 which may be of the centrifugal type is connected toconduit 50 to pressurize the fuel therein. A conventional afterburnerfuel meter generally indicated by 54 is responsive to selected engineoperating conditions which may include the position of a control lever56 and is connected to conduit 50 in flow controlling relationshiptherewith. The afterburner fuel meter 54 may include a variable areametering valve 58 in flow controlling relationship with conduit 50. Awash type filter 60 is disposed in conduit 50 upstream from valve 58. A

fuel cut-off valve 62 suitably located in conduit 50 and actuated bycontrol lever 56 serves to establish or disestablish flow throughconduit 50 depending upon the position of control lever 56.

The afterburner air-fuel mixture is ignited by convventional ignitionmeans generally indicated by 64 which may include a suitable electricpower source 66 connected to energize a spark producing element 68suitably located in casing 22 to thereby ignite the afterburner air-fuelmixture in response to a control signal derived from afterburner fuelmanifold flow sensor and igniter control generally indicated by 70.

It is desirable to ignite the afterburner as soon as possible inresponse to movement of control lever 56 to a position requestingafterburner operation. However, positive and reliable ignition of theair-fuel mixture cannot be realized until the afterburner fuel manifold40 is adequately pressurized with fuel thereby ensuring that the fuelinjected through nozzles 42 is of sufficient quantity to establish theproper afterburner air-fuel ratio necessary for substantiallyinstantaneous combustion. To that end, the afterburner fuel manifoldflow sensor and igniter control 70 senses the quantity of metered fuelflow supplied to the afterburner fuel manifold 40 the known volume ofwhich becomes filled upon receiving a predetermined quantity of fuelthereby pressurizing the fuel injection nozzles 42 to the extentrequired to establish the desired air fuel ratio for ignition purposes.The control 70 generates an output signal upon sensing the predeterminedquantity of metered afterburner fuel flow to energize the ignition means64 for a predetermined time period to ignite the afterburner air-fuelmixture The afterburner fuel manifold flow sensor and igniter control 70includes a casing 72 having an inlet port 74 connected via a passage 76to conduit 50 at fuel pressure P upstream from filter 60, an inlet port78 connected via passage 80 to conduit 50 at unmetered fuel pressure P,downstream from filter 60 and an inlet port 82 connected via passage 84to conduit 50 at metered fuel pressure P downstream from afterburnerfuel meter 54. Fuel at pressure P entering casing 72 via port 74 passesthrough a filter 86 contained by a chamber 88 to a passage 90 containinga restriction 91 and connecting chamber 88 with a chamber 92 thenthrough a passage 94 containing a valve orifice 96 to a chamber 98partially defined by a piston 100. A passage 102 containing a springloaded check valve 104 connects chambers 88 and 92 which check valve 104permits flow only from chamber 92 to chamber 88. Fuel at pressure Pentering casing 72 via port 78 passes to a chamber 106 which isseparated from chamber 92 by a diaphragm 108. The diaphragm 108 isfixedly secured at its radially outermost portion to casing 72 and issecurely clamped between backing plates 110 and 112 by rivet means 114one portion of which defines a valve element 116. The valve element 116is adapted to seat against valve orifice 96 in response to movement ofdiaphragm 108 to control the effective flow area of orifice 96 and thusthe flow therethrough accordingly.

The piston 100 is slidably carried in casing 72 and separates chamber 98from a chamber 118 vented to metered fuel pressure P via a passage 120leading to inlet port82. Piston 100 is urged into engagement with anadjustable stop 122 threadedly engaged with casing 72 by a spring loadedrod 124 having a curved end portion 126 bearing against piston 100. Therod 124 is slidably mounted for guided movement in a fixed sleeveportion 128 through which the rod 124 extends. A compression spring 130is interposed between spring retainers 132 and 134 integral with curvedend portion 126 and sleeve 128, respectively. As will be describedhereinafter, the piston is urged off stop 122 against the resistance ofspring by the pressure differential P,40 P generated across piston 100which moves axially until an annular beveled end portion 136 thereofengages a fixed stop 138 having an annular recessed portion 140 adaptedto receive an annular ring seal 142 of resilient material provided witha beveled edge against which the beveled end portion 136 of piston 100bears to establish a positive fluid seal against leakage from chamber 98to chamber 118.

The rod 124 is adapted to engage one end of a circular level 144 whichextends through an opening 146 in casing 72 separating chamber 118 froma chamber 148 and is mounted for pivotal movement on a pin 150 securedto casing 72. The opening 146 is larger than lever 144 to permit alimited range of pivotal movement of lever 144 on pin 150. An O-ring 151suitably secured in a recess in casing 72 provides a resilient sealagainst fuel leakage between adjacent surfaces of opening 146 and lever144. The one end of lever 144 extends into chamber 148 which is ventedvia a passage 152 to an outlet port 154 in casing which, in turn, isvented via a passage 155 to a suitable drain source at relatively lowfluid pressure P such as conduit 50 at the inlet to pump 53. A half ballservo valve 156 actuated by lever 144 is carried by an adjustableretaining member 158 which is threadedly engaged with the end of lever144. A spring 160 interposed between casing 72 and lever 144 preloadslever 144 thereby urging half ball valve 156 against a valve orifice 162to close the same.

A stepped diameter piston 164 slidably carried in casing 72 separateschamber-148 from a chamber 166. Chamber 166 is vented to receive fuel atregulated substantially constant pressure P, from an inlet port 168 viaa passage 170 containing a filter 172, an annulus 174 partially deformedby the intermediate step of piston 164 and a passage 176 containing arestriction 178. The inlet port 168 is connected via passage 170 to asuitable source 181 of fuel at regulated constant pres sure P Chamber166 discharges fuel to chamber 148 via a passage 180, an annulus 182formed in a valve 184 slidably carried in casing 72, and a passage 186having valve orifice 162 connected to the discharge end thereof. Flowthrough passage is interrupted by the large diameter portion of piston164 which slides axially to cover the one end of passage 180 therebyblocking communication between chamber 166 and passage 180. Flow throughpassage 180 is also interrupted by the valve 184 which slides axiallycarrying annulus 182 out of registration with the adjacent end ofpassage 180 thereby blocking the same.

A tubular member 186' having a transverse wall 188 is fixedly secured tocasing 72 by any suitable means such as a plurality of bolts 190 passingthrough flanged portion 192 thereof into threaded engagement with casing72. The tubular member 186' is axially aligned with piston 164 which isadapted to slide over the member 186 to the extent permitted by thelarge diameter end of piston 164 which may abut a fixed stop 196 definedby casing 72. A compression spring 194 interposed between flangedportion 192 and piston 164 applies a preload against the latter to seatthe same against suitable stop means 198 defined by casing 72.

The chamber 166 is vented to the interior of tubular member 186 via apassage 199 in the wall thereof which interior is vented to a chamber200 at fuel pressure P via a valve orifice 202 fixedly secured by anysuitable means such as a press fit to the inner wall of tubular member186 in spaced axial relationship to wall 188. A valve 204 slidablycarried in tubular member 186' is urged into seating engagement onorifice 202 by a compression spring 206 interposed between casing 72 andvalve 204 to thereby close orifice 202. Fuel at pressure P passingthrough open orifice 202 passes through valve 204 via a passage 208connecting opposite faces thereof. The chamber 200 is vented to chamber148 via a passage 210 containing a variable area flow restriction 212the effective area of which is established by an adjustable valve 214threadedly engaged with casing 72.

The valve 184 is slidably carried in a chamber 216 and biased in onedirection axially by a compression spring 218 interposed between casing72 and one end of valve 184. The opposite end of valve 184 is providedwith a recess 220 containing a resilient-seal member 222 adapted to seatagainst a valve orifice 224 leading from chamber 216 to passage 170. Apassage 226 is adapted to vent one end of chamber 216 to passage 170 atregulated pressure P depending upon the position of piston 164 the largediameter portion of which slides relative to passage 226 to establish ordisestablish flow therethrough. The opposite end of chamber 216 isvented via a passage 228 to passage 210 at pressure P The opposite endsof chamber 216 communicate via an axial passage 230, a radial passage232 which terminates in an annulus 234, and a passage 236 formed invalve 184. The valve 148 is provided with a valve orifice 238 at one endof axial passage 230 which valve orifice is adapted to seat against aresilient seal member 240 contained by a recess 242 in casing 72 toblock flow through passage 230 when valve 184 is pressurized to theright in a manner to be described. The annulus 234 in the position ofvalve 184 shown communicates with a passage 244 in casing 72 leading toan outlet port 246 which, in turn, is connected via passage 247 toexhaust nozzle control 48.

Referring back to tubular member 186 and the valve 204 slidably carriedtherein, the valve 204 is provided with a stem or rod portion 248integral therewith and extending axially therefrom through valve orifice202 into sliding engagement with an opening 250 in transverse wall 188.The end of stem 248 is adapted to be engaged by an abutment 252 definedby one arm of a pawl member 254 pivotally carried on a pin 256 which, inturn, is secured to piston 164. A compression spring 258 interposedbetween the closed end of piston 164 and an arm 260 of pawl member 254serves to resiliently load the latter causing an arm 262 thereof toengage piston 164 thereby aligning stop 252 with stem 248. The arm 260is adapted to be engaged by tubular member 186' as piston 164 movesrelative thereto to pivot pawl member 254 causing stop 252 to disengagestem 248.

A stem or rod portion 264 threadedly engaged at one end to piston 164extends axially therefrom into sliding engagement with casing 72 and isprovided with a cam portion 266. A cam follower defined by a ball 268retained in a recess 270 partially defined by casing 72 bears againstcam portion 266 which is adapted to urge ball 268 radially outwardlytherefrom into engagement with one end of a pin 272 slidably carried ina guide 274 threadedly engaged with casing 72. The opposite end of pin272 engages an adjustable member 276 threadedly engaged with one end ofa lever 278 to thereby pivot lever 278 against the resistance of acompression spring 280 interposed between the opposite end of lever 278and casing 72. The lever 278, in turn, simultaneously actuates twoelectrical switches generally indicated by 282 which, in turn, are wiredto provide an electrical input signal to the afterburner igniterapparatus.

The lever 278 extends through an opening 284 in casing 72 and ispivotally mounted for limited movement on a pin 286 suitably secured tocasing 72. An 0 ring seal 288 suitably carried in the wall of opening284 serves as a resilient seal against fluid leakage between fuel atpressure P and air at atmosphere pressure on opposite sides of opening284. A plug 290 threadedly engaged with casing 72 provides for access toadjustable member 276 for calibration purposes.

OPERATION Referring to FIG. 1, it will be understood that the variouscontrol fuel pressures within the casing 72 do not differ to anysubstantial degree and are at a relatively low value as a result of thecontrol lever 56 being in a non-afterburning or dry engine position.

Referring to FIG. 2, it will be assumed that the control lever 56 isactuated to a position requesting afterbuming or wet engine operation.The afterburner fuel cut-off valve 62 opens accordingly to permit fuelat pump discharge pressure P to pass through conduit 50 to meteringvalve 58 which occupies a predetermined position as a function of theengine operating conditions including position of control lever 56thereby establishing the effective flow area of conduit 50 and thusmetered fuel flow to the afterburner manifold 40.. The fuel passesthrough filter 60 undergoing a drop from pressure P to P and thenthrough metering valve 58 undergoing a corresponding pressure drop fromP to P Fuel at pressure P enters chamber 88 where it is filtered andsubsequently passes through metering restriction 91 to chamber 92 thenthrough orifice 96 and passage 94 to chamber 98. Fuel at pressure Penters chamber 106 where it acts against diaphragm 108 in opposition topressure P generated in chamber 92 which diaphragm 108, in turn,positions valve 116 to throttle flow through orifice 96 and regulate thefuel pressure P in chamber 92 to equal fuel pressure P The pressure dropP,P, across the metering orifice 96 is equal to the pressure drop P Pacross the filter 60 which establishes a flow through meteringrestriction 91 and thus through orifice 96 to chamber 98 in directproportion to the flow through conduit 50 to fuel manifold 40. Thepiston 100 responds to the pressurized flow into chamber 98 and moves tothe right against the spring 130 augmented by the force of pressure P,.acting against piston 100 with a velocity directly proportional to theflow into chamber 98 (see FIG. 3). Since all of the flow throughmetering restriction 91 passes to chamber 98, the piston 100 moves untilthe end portion 136 thereof engages seal 142 on stop 138 which occurswhen a known quantity of metered fuel has passed through restriction 91.Thus, the piston 100 acts as a flow measuring device. The relationshipof the flow through metering restriction 91 and the flow through conduit50 to the fuel manifold is directly proportional to the flow arearelationship between the restriction 91 and the filter 60. For example,assume the metering area of restriction 91 is 5.0 percent of theeffective area of filter 60 and the total displacement of piston 100 is5. percent of the volume of fuel manifold 40. With the fuel manifold 40empty at the time of opening cut-off valve 62, the piston 100 will bedisplaced from stop 122 to stop 138 during the time fuel manifold 40 isfilled with the piston 100 engaging stop 138 at the same time manifold40 becomes lpercent filled. The stop 122 may be adjusted to establishthe starting position of piston 100 which, in turn, determines theeffective displacement thereof and thus the quantity of flow intochamber 98 to fully displace piston 100 against stop 138. With piston100 fixed against stop 138, flow into chamber 98 ceases causingpressures P, in chamber 98 to rise to pressure P,. The resulting P,-Pacross diaphragm 108 urges diaphragm 108 toward chamber 106 causingvalve 116 to fully open and plate 110 to engage casing 72 therebypreventing flexing of diaphragm 108 beyond its capabilities.

With the fuel manifold 40 filled, the afterburner fuel ignitionmechanism is set in operation (see FIG. 4). To that end, as piston 100approaches stop 138, the rod 124 which follows piston 100 engages theend of lever 144 causing clockwise movement thereof as viewed in FIG. 4which, in turn, lifts valve 156 off orifice 162 thereby venting passage186 to chamber 148 at pressure P The resulting drop in pressure P,, inchamber 166 intermediate restriction 178 and orifice 162 allows piston164 to move off stop 198 against the resistance of spring 197 under theinfluence of pressure P,. acting against the stepped portion of piston164 defining an nulus 174. Continued movement of piston 164 results inengagement of pawl abutment 252 with stem 248 and movement of camportion 264. The cam portion 264 urges follower ball 268 into engagementwith pin 272 which, in turn, is driven axially into engagement withmember 276 carried by lever 278 causing lever 278 to pivotcounterclockwise and actuate switches 282 to a closed position tothereby energize the electrical igniter of the afterburner.

The electrical igniter remains energized for a predetermined timeinterval as a result of control over the flow out of chamber 166 via theadjustable orifice 214 (see FIG. To that end, the movement of piston 164results in the large diameter portion of piston 164 sliding over theadjacent end of passage 180 to block the same immediately afterengagement of pawl abutment 252 with stem 248. The abutment 252 drivesstem 248 and attached piston 204 against the resistance of spring 206thereby opening orifice 202 to vent chamber 166 to chamber 166 tochamber 200 from which flow is controlled by adjustable orifice 212 inpassage 210 leading to chamber 148 at pressure P The effective flow areaof orifice 212 established by the setting adjusting valve 214 determinesthe flow out of chamber 166 upon which the velocity piston 164 isdependent. Thus, the time interval required by the piston 164 tocomplete its stroke may be varied as desired to maintain the afterburnerigniter energized. As the piston 164 continues to move, the arm 260 ofpawl 254 engages tubular member 186 which urges pawl 254 clockwisemoving abutment 252 out of contact with stem 248 allowing piston 204 tomove against orifice 202 under the influence of spring 206 therebyblocking flow out of chamber 166 causing the pressure P,, therein torise accordingly. The rise in pressure P,, in chamber 166 causes piston164 to stop and reverse in motion and subsequently engage stop 198. Thecam portion 266 carried by piston 164 moves accordingly to allowfollower ball 268 and pin 272 to drop and permit lever 278 to pivotclockwise under the influence of spring 280 thereby opening switches 282which, in turn, de-energizes the afterburner igniter (see FIG. 6

As the piston 164 is activated against spring 197 during the timedignition process, a pressure signal is generated to release the exhaustnozzle gates 44 in accordance with afterburning requirements (see FIG.5). To that end, the one end of passage 226 is uncovered by the trailingedge of the large diameter portion of piston 164 as the pistonapproaches the limit of its travel to the right as viewed in FIG. 5.Fuel at pressure P, is vented through passage 226 to the left-hand endchamber 216 where it acts against valve 184 driving the same against theresistance of spring 218 thereby causing orifice 238 to seat againstseal member 240 to isolate passage 230 form the right-hand end ofchamber 216 at pressure P The annulus 182 in valve 184 moves out ofcommunication with passages 180 and 186 thereby blocking the same. Fuelat pressure P, passes through orifice 224 which is fully open to theleft-hand end of chamber 216 thereby providing a source of pressure P,in parallel to passage 226. The annulus 234 in valve 184 moves out ofcommunication with passage 244 which is subsequently vented past thetraveling edge of valve 184 to the lefthand end of chamber 216 atpressure P, thereby establishing a pressure P, signal at port 246 whichis transmitted via passage 247 to exhaust nozzle control 48 to effectrelease of the nozzle gates 44.

When the piston 164 reverses its direction of movement and moves backtoward stop 198, the valve 184 remains pressurized to the right bypressure P, (see FIG. 6). 'It will be noted that the passage 226 isblocked by the large diameter portion of piston 164 as the piston moveson its return stroke thereby isolating passage 226 from passage 170 atpressure P,. However, the left-hand end of chamber 216 is vented topressure P, via orifice 224 which maintains valve 184 in the biasedposition against seal member 240.

FIG. 7 illustrates the positions occupied by the various componentmembers upon completion of the heretofore described afterburner ignitioncycle. It will be noted that piston remains pressurized against stop 138by the P P pressure differential existing thereacross. Any tendency forleakage of the relatively high pressure fuel at pressure P past piston100 to chamber 118 at pressure P, is resisted by the seal 142 whichbecomes more positive as the pressure differential P P increases.

Referring to FIG. 8, the piston 100 is returned to its position againststop 122 by actuating control lever 56 to a non-afterburning or dry"engine position. Assuming the control lever 56 is actuated to a dryengine position, the cut-off valve 62 is closed accordingly, whereuponthe fuel pressures in chamber 118, 88, 106, 92 and 98 equalize. Thespring 130 urges piston 100 toward stop 122 whereupon fuel in chamber 98is forced through orifice 96 to chamber 92. The time required for piston100 to move into engagement with stop 122 is minimized by the checkvalve 104 which opens to vent chamber 92 to chamber 88 in parallel flowrelationship with metering restriction 91. As the piston 100 returns tostop 122, the stem 124 becomes disengaged with lever 144 allowing spring160 to bias lever 144 in a direction to close valve 156.

When the control lever 56 is reset in the abovementioned manner todiscontinue afterburner operation, the valve 184 is caused to return toits position to the left where seal 222 engages orifice 224. To thatend, movement of control lever 56 causes port 168 to be vented fromregulated pressure P, to relatively low pressure P The resulting drop inpressure in chamber 216 adjacent orifice 224 permits valve 184 to moveto the left under the influence of spring 218 thereby urging seal 222into engagement with orifice 224 to block the same. The right-hand endof chamber 216 being vented to pressure P via passages 228 and 210communicates with the left-hand end of chamber 216 via passages 230, 232and 236 thereby balancing the pressures across valve 184 as well asreducing the pressure signal at port 246 from P, to P by virtue of theannulus 234 communicating passage 232 with passage 224.

Referring to FIG. 9, it may be undesirable to use a mechanical cam andfollower such as cam portion 266, follower ball 268 and pin 272 toactuate the switches 282 for reasons apparent to those skilled in theart. If desired, the switches 282 may be actuated by fuel servo operatedmechanism as indicated in FIG. 9 wherein a portion of the afterburnerfuel manifold flow sensing and igniter control 70 is broken away to showthe modified portion thereof. The remaining portion of the control 70 isidentical to that shown in FIGS. 1 through 8.

Referring to FIG. 9, a stepped diameter piston 292 is provided with alarge diameter portion 294 slidably carried in a chamber 294 which isvented via a passage 296 to passage 180. The small diameter portion 298of piston 292 extends through an end wall 300 of chamber 294 into achamber 302 vented to chamber 148 at pressure P via a passage 304. Atransverse annular section 306 between the large and small diameterportions of piston 292 is vented via an annulus 308 and passage 310 topassage 176 upstream from restriction 178. The lever 278 is providedwith a slotted end 312 pivotally mounted on a pin 314 secured to thesmall diameter portion 298 of piston 292. An adjustable stop 316threadedly engaged with casing 72 is engaged by the 6 in movement in theopposite direction by a stop member 320 fixedly secured to piston 292and adapted to engage the end wall of chamber 294.

The passage 296 is vented via a passage 322 to a port 324 in the wall ofchamber 166 which port 324 is adapted to be blocked or vented to chamber148 depending upon the position of piston 164 as will be described.

The operation of FIG. 9 is best described in relation to FIG. 2 through8 and the sequence of movement of piston 164 associated therewith.Beginning with the afterbumer-fuel manifold flow sensor and igniter inthe non-afterburning or dry" engine condition as represented by FIG. 2,the piston 292 is pressurized against stop 316 by fuel at pressure P, inchamber 294 which augments spring 318 in opposition to the relativelysmaller force generated by pressure P acting against transverse section306. It will be noted that chamber 294 is vented to pressure P, byvirtue of the piston 164 blocking port 324 thereby preventingcommunication of passage 296 at pressure P, with chamber 148 atrelatively lower pressure P Referring to FIG. 4, as the piston 164 ispressurized against spring 197 causing the large diameter portion ofpiston 164 to slide over the adjacent end of passage 180, the trailingedge of the smaller diameter portion of piston 164 subsequently uncoversport 324 to vent passage 296 to chamber 148 at pressure P It will beunderstood that the spacing of passage and port 324 is such that piston164 closes passage 180 before opening port 324. The resulting drop infuel pressure to P in chamber 294 allows pressure P, acting againsttransverse section 306 to overcome spring 318 driving piston 292 untilstop member 320 engages casing 72. The lever 278 follows piston 292 toactivate switches 282 to an open position thereby energizing theafterburner igniter.

As described in connection with FIGS. 5 and 6, the afterburner igniterremains energized for a predetermined time interval and is de-energizedupon reverse motion of piston 164. To that end, reverse motion of piston164 results in the small diameter portion of piston 164 sliding overport 324 to block the same in advance of the larger diameter portion ofpiston 164 sliding over the end of passage 180 to open the samewhereupon the pressure in passage 296 and thus chamber 294 rises topressure P, causing piston 292 to move against stop 316 which, in turn,results in movement of lever 278 to activate switches 282 to a closedposition thereby de-energizing the afterburner igniter.

While my invention is described in a preferred embodiment for use withafterburner fuel flow sensing and igniting purposes, it will berecognized that it may be readily adapted for use in any system where itis desired to accurately sense a predetermined quantity of a firstmetered flow and subsequently provide a control signal of predeterminedtimed duration to control a second flow as, for example, in fluid batchprocessing.

Iclaim:

1. Fuel flow sensing apparatus for measuring fuel flow through a supplyconduit to a jet engine afterburner fuel manifold having a known volume,said fuel flow sensing apparatus comprising:

flow restricting means in series flow relationship with said conduit;

means defining a variable volume chamber;

displaceable pressurized fuel flow responsive means in said chamber;

passage means communicating said chamber with said conduit upstream fromsaid flow restricting means;

a metering restriction having a predetermined effective flow arearelative to the flow area of said flow restricting means in said passagemeans for controlling fuel flow therethrough;

valve means operatively connected to said passage means for controllingthe fluid pressure differential across said metering restriction; and

fuel pressure responsive means operatively connected to said valve meansand responsive to the fluid pressure differential across said flowrestricting means for controlling said valve means to establish a commonpressure differential across said metering restriction and said flowrestricting means;

said displaceable flow responsive means being responsive to thepressurized fuel flow through said passage means to said chamber anddisplaceable as a known function of the rate of fuel flow through saidmetering restriction; and

fuel flow igniting means operatively connected to said displaceablemeans for igniting the afterburner fuel flow upon movement of saiddisplaceable means to a predetermined position.

2. Fuel flow sensing apparatus as claimed in claim 1 wherein:

said operative connection between said flow igniting means and saiddisplaceable mans includes second fluid pressure responsive means havinga first position;

passage means for supplying pressurized fluid to said second fluidpressure responsive means for actuatin g the same;

second valve means operatively connected to said last named passagemeans for controlling the fluid pressure to which said second fluidpressure responsive means responds to initiate movement thereof fromsaid first position to energize said igniting means;

means including a lost motion connection between said second valve meansand said displaceable flow responsive means for actuating said secondvalve means following movement of said displaceable flow responsivemeans to a predetermined position corresponding to the volume of fuelrequired to fill said afterburner fuel manifold to a predeterminedextent; and

means operatively connected to said second fluid pressure responsivemeans and said passage means for controlling the fluid pressure to whichsaid second fluid pressure responsive means responds to control the rateof movement of said second fluid pressure responsive means from saidfirst.

position to a second position. v 3. Fuel flow sensing apparatus asclaimed in claim 2 wherein:

4. Fuel flow sensing apparatus as claimed in claim 1 wherein:

said operative connection between said igniting means and saiddisplaceable means includes output signal generating means connected toenergize said igniting means;

piston means connected to said output signal generating means foractuating the same;

conduit means connecting a first source of pressurized fluid with asecond source of relatively lower pressure fluid;

a fluid flow restriction in said conduit means for controlling flowtherethrough;

valve means downstream from said fluid flow restriction and in seriesflow relationship therewith for controlling the fluid pressureintermediate said fluid flow restriction and said valve means dependingupon the position of said valve means;

said valve means being operatively connected to said displaceable meansand actuated thereby;

said piston means being responsive to said fluid pressure intermediatesaid fluid flow restriction and said valve means.

5. Fuel flow sensing apparatus as claimed in claim 4 and furtherincluding:

branch conduit means connected to said conduit means intermediate saidfluid flow restriction and said valve means and arranged in parallelflow relationship with said valve means;

normally closed valve means in said branch conduit means forestablishing and disestablishing flow therethrough depending upon theposition of the same in response to said piston means;

an adjustable fluid flow restriction in said branch conduit means inseries flow relationship with said normally closed valve means forcontrolling the rate of fluid flow through said branch conduit meansfollowing movement of said normally closed valve means to an openposition;

said piston means being activated from a first position by saidintermediate fluid pressure in response to movement of said first namedvalve means and operative to subsequently block said conduit means andactivate said normally closed valve means to an open position whereuponsaid piston means moves at a predetermined rate depending upon thesetting of said adjustable flow restriction to a predetermined secondposition where said normally closed valve means is actuated by saidpiston means to a closed position to effect return of said piston meansto said first position.

6. Fuel flow sensing apparatus as claimed in claim 5 wherein:

wherein:

said second valve means is actuated by a spring loaded lever to a closedposition; said lever having a spaced-apart relationship with saiddisplaceable means defining said lost motion connection and beingengaged by said displaceable means to activate said second valve meansto an open position.

1. Fuel flow sensing apparatus for measuring fuel flow through a supply conduit to a jet engine afterburner fuel manifold having a known volume, said fuel flow sensing apparatus comprising: flow restricting means in series flow relationship with said conduit; means defining a variable volume chamber; displaceable pressurized fuel flow responsive means in said chamber; passage means communicating said chamber with said conduit upstream from said flow restricting means; a metering restriction having a predetermined effective flow area relative to the flow area of said flow restricting means in said passage means for controlling fuel flow therethrough; valve means operatively connected to said passage means for controlling the fluid pressure differential across said metering restriction; and fuel pressure responsive means operatively connected to said valve means and responsive to the fluid pressure differential across said flow restricting means for controlling said valve means to establish a common pressure differential across said metering restriction and said flow restricting means; said displaceable flow responsive means being responsive to the pressurized fuel flow through said passage means to said chamber and displaceable as a known function of the rate of fuel flow through said metering restriction; and fuel flow igniting means operatively connected to said displaceable means for igniting the afterburner fuel flow upon movement of said displaceable means to a predetermined position.
 2. Fuel flow sensing apparatus as claimed in claim 1 wherein: said operative connection between said flow igniting means and said displaceable mans includes second fluid pressure responsive means having a first position; passage means for supplying pressurized fluid to said second fluid pressure responsive means for actuating the same; second valve means operatively connected to said last named passage means for controlling the fluid pressure to which said second fluid pressure responsive means responds to initiate movement thereof from said first position to energize said igniting means; means including a lost motion connection between said second valve means and said displaceable flow responsive means for actuating said second valve means following movement of said displaceable flow responsive means to a predetermined position corresponding to the volume of fuel required to fill said afterburner fuel manifold to a predetermined extent; and means operatively connected to said second fluid pressure responsive means and said passage means for controlling the fluid pressure to which said second fluid pressure responsive means responds to control the rate of movement of said second fluid pressure responsive means from said first position to a second position.
 3. Fuel flow sensing apparatus as claimed in claim 2 wherein: said last named means includes a normally closed valve member and an adjustable flow restricting orifice downstream therefrom in parallel flow relationship with said second valve means.
 4. Fuel flow sensing apparatus as claimed in claim 1 wherein: said operative connection between said igniting means and said displaceable means includes output signal generating means connected to energize said igniting means; piston means connected to said output signal generating means for actuating the same; conduit means connecting a first source of pressurized fluid with a second source of relatively lower pressure fluid; a fluid flow restriction in said conduit means for controlling flow therethrough; valve means downstream from said fluid flow restriction and in series flow relationship therewith for controlling the fluid pressure intermediate said fluid flow restriction and said valve means depending upon the position of said valve means; said valve means being operatively connected to said displaceable means and actuated thereby; said piston means being responsive to said fluid pressure intermediate said fluid flow restriction and said valve means.
 5. Fuel flow sensing apparatus as claimed in claim 4 and further including: branch conduit means connected to said conduit means intermediate said fluid flow restriction and said valve means and arranged in parallel flow relationship with said valve means; normally closed valve means in said branch conduit means for establishing and disestablishing flow therethrough depending upon the position of the same in response to said piston means; an adjustable fluid flow restriction in said branch conduit means in series flow relationship with said normally closed valve means for controlling the rate of fluid flow through said branch conduit means following movement of said normally closed valve means to an open position; said piston means being activated from a first position by said intermediate fluid pressure in response to movement of said first named valve means and operative to subsequently block said conduit means and activate saiD normally closed valve means to an open position whereupon said piston means moves at a predetermined rate depending upon the setting of said adjustable flow restriction to a predetermined second position where said normally closed valve means is actuated by said piston means to a closed position to effect return of said piston means to said first position.
 6. Fuel flow sensing apparatus as claimed in claim 5 wherein: said first and second sources of pressurized fluid are fuel.
 7. Fuel flow sensing apparatus as claimed in claim 1 wherein: said second valve means is actuated by a spring loaded lever to a closed position; said lever having a spaced-apart relationship with said displaceable means defining said lost motion connection and being engaged by said displaceable means to activate said second valve means to an open position. 